Fluid container



Feb. 8, 1966 N. A. ZEPELL 3,

FLUID CONTAINER Original Filed April 28, 1961 2 Sheets-Sheet 1 6 58 6: ii 54 g 72 [W 4 50 F/G 2 K E h 24 32 as 34 INVENTOR. F/G. NATHA/V ALTERZEPELL N. A. ZEPELL Feb. 8, 1966 l-LUID CONTAINER Sheets-Sheet 2Original Fihul April 38, 1961 INVENTOR. ,ll'. 7":H ZEPELL of a user.

3,233,594 FLUID CONTAINER "Nathan Alter Zepell, Chicago, 111., assignorto w. A.

Sheaifer' Pen Company, Fort Madison, Iowa, a corporation of DelawareContinuation of application Ser. No. 106,312, Apr. 28, 1961. Thisappiication Apr. 24, 1964, Ser. No. 363,678

3 Claims. (Cl. 120--45.4)

This application is a continuation of application Serial Number 106,312,filed April 28, 1961, now abandoned. The invention relates to acontainer for liquids, and more particularly to a fluid reservoir havinga wall member which is displaceable to reduce the capacity of thereservoir in response to the withdrawal of fluid there body portion toreduce the volumetric capacity of the reservoir in response to thewithdrawal of fluid therefrom.

The reservoir of the usual fountain pen or similar implement remainsunchanged as to capacity during normal .useair entering the reservoir torep-lace fluid as it is withdrawn during writing. Because of thedifference in density between air and liquid, the air entering thereservoir rises above-the writing fluid and remains thereaboveregardless of the position in which the fountain pen sub-, sequently maybe held.

The air thus present in the reservoir of a writing implement will expandor contract if subjected to changes in temperature and/ or atmosphericpressure.

A decrease in atmospheric pressure or an increase in- -temperatureeasily may cause an undesirable condition in the usual pen should it bepositioned point downwardly,

. as in writing; Under these conditions, a quantity of fluid,

equal to the increase in air volume, will be forced from the reservoirand into the expansion chambers of the feed. If such expansion chambersare not of suflicient capacity, a portion of this fluid may drip fromthe implement into the cap-or blot the writing surface or soil the usershands or clothing. This problem of expansion is encountered particularlyduring air travel, in which great extremes of temperature and pressureare encountered in relatively short periods of time. However, if a penis positioned point upwardly when the above described expansion of airoccurs, the excess air in the reservoir will escape readily through thefeeding passageways without causing leakage.

In addition, as is well understood in the art, present day fountain pensare limited as to capacity because of the above described problem ofexpansion of air which may be trapped above the fluid. This factorrequires relatively frequent refilling of the pen on the part of theuser.

These problems long have been recognized in the art, and a number ofproposals have been made for their solution. For example, it has beenproposed to use valves to prevent leakage and flooding while stillallowing'for a large capacity. However, such proposals have not beenmanufactured commercially because of complications in manufacture andsubsequent operation while in the hands Capillary storage cuts have beenused in the feed of a fountain pen to partially compensate for expansionof air in the reservoir, but such an arrangement does not eliminate theproblem of expansion nor does it provide for a large controlled fluidcapacity.

Accordingly, it is a principal object of this invention to provide afluid reservoir for a fountain pen or the like,

United States Patent C 3, 33,594 7 Patented Feb. 8, 1966 which reservoiris not subject to leaking and flooding as a result of temperature orbarometric pressure changes.

' Another object of this invention is to provide a fluid reservoir whichhas a large capacity but which is not affected by temperature orbarometric pressure fluctuations.

A further object of this invention is to provide a fluid reservoir whichhas a flexible wall member adapted to follow the fluid and reduce thevolumetric capacity of the reservoir as the fluid is withdrawntherefrom.

A still further object of this invention is the formationof a reservoirhaving a'body portion releasably engaging a flexible wall member of theabove described character, which wall member may be formed directlywithin the body portion, thereby eliminating the necessity of anyassembly thereof.

Yet another object of this invention is the provision of a fountain penreservoir of the above character which is furnished in the form of acartridge unit.

Further and additional objects of this invention will be apparent fromthe following description when taken with the accompanying drawings.

In accordance with one embodiment of the invention the fountain pencomprises a fluid container and a writing unit assembly mountedforwardly thereof, the fluid container having a vented hollow bodyportion and a filmlike layer of flexible material forming a flaccid sackengaging and releasably adhering to the interior surface of the bodyportion. The interior surface of said sack defines a Writing fluidreservoir, and the unit assembly has conduit means providing the solefluid lead or leads from said writing fluid reservoir. The conduit meansis small enough in cross-section to prevent rearward movement of airtherethrough into the reservoir while there is writing fluid within theconduit;.tha-t is, air will not bubble through to the reservoir as itdoes in the usual fountain pen. T he adherent attachment of the sack tothe interior surface of the body portion is suflicient to resistseparation thereof and the consequent free discharge of writing fluidthrough the conduit under the influence of the normal weight of saidcolumn. However, the sack is separable from and displaceable within thebody portion to reduce the volumetric capacity of the reservoir inresponse to forcible withdrawal of writing from the conduit by capillaryaction as during writing.

In the drawings:

FIGURE 1 is a greatly enlarged broken longitudinal sectional view of acartridge barrel unit embodying a preferred form of the presentinvention; 1

FIG. 2 is a reduced longitudinal sectional view similar to FIG. 1 of thecartridge barrelunitthereof, assembled with the writing unit of afountain pen, with the fluid supply being partially depleted;

FIG. 3 is a longitudinal sectional view of another embodiment of thepresent invention, showing a cartridge unit partially assembled with afountain pen;

FIG. 4 is a fragmentary sectional view of the rearward portion of FIG.3, showing the venting of the cartridge unit;

FIG. 5 is a sectional view along the line 5-5 of FIG. 3;

FIGS. 6, 7 and 8 are views in longitudinal cross section, showing stepsin the manufacture of the cartridge barrel unit of FIG. 1; and

FIG. 9 is a fragmentary sectional view of the rearward portion of thecartridge unit of the embodiment of FIG. 3, showing the holder orcarrier utilized during formation of the flexible wall member.

Referring now to the drawings and particularly to FIGS. 1 and 2 thereof,there is provided a fountain pen cartridge unit 10 having a body orsupport portion 12 molded or otherwise formed of a durable, relatively.anaperture "18 defining a vent passage between the exterior and theinterior of the body portion '12.

Disposed within and releasably supported by the body portion 12 is a-flexible orflaccid wall member 20 which ,may beformed ofany one ofanumber of materials, as

will be'indicated in more detail herebelow. The wall member 20 isslightly adherent to the body portion .12, and preferably relativelythin. It is shown in the drawings as being proportionately thicker thanit normally would be in actual practice, in order to clearly disclosethe character thereof. Generally, the wall member may range between.001" to .010" in thickness, although it is understood that thethickness thereof is not to be limited to this range as it may be varieddepending upon the material from which it is formed and the fluidfeeding characteristics desired.

In this embodiment of the invention, the flexible or flaccid wall member20 is shown in the general shape of the usual cylindrical ink reservoirsac, having a closed end 22 and an open end 24. The closed end 22 ispositioned at the closed end 16of the body portion 12, with its .openend '24 beingpositioned at the open end 14 of thebody portion.Accordingly, the flexible wall member 2%, in effect, forms a liner.within the body portion to provide a laminated reservoir section.Disposed within the body portion 12 adjacent its forward end 14 is athinjband of adhesive or primer 26 which forms a permanent'bond betweenthe body portion 12 and wall portion '20 adjacent their forward ends 14and 24, respectively.

The reservoir thus defined by the interior surface of the flexible wallmember 20 is intended to be filled with aliquid, such ,as an ink of thetype used in pens. Therefore, in order to close the forward end of thebody portion 12 and .wall portion 20, there is provided means comprisinga closure disc28 having a flange 30 and a rearwardly extending centerportion 32. The flange 30 is bonded to the forward end 14 of the bodyportion 12 as by heat sealing. The closure disc 28 is provided with acentrally disposed circular recess or discharge 34 which defines a thindiaphragm '36 pierceable readily by a pointed tubular member such asthose used in present day cartridge type fountain pens.

The outer surface of the flexible wall member 20 is engaged in intimatecontact with the interior surface of the body portion .12 throughout theentire surface area thereof. When thus engaged, the flexible wall member20 is in an unstressed or neutral condition andexerts no appreciablepressure on the liquid disposed therein. Ac-

cordingly, at no time, does .it have a tendency to force fluid from .thereservoir even when the reservoir .is open and in use in a fountain penor similar implement. In fact, because of theslight adherent attractionbetween the wall member 20 and the body portion 12, the wall member, asoutlined in more detail hereinbelow, will tend to create aslightnegative pressure in the reservoir (2. pressure below normal airpressure) as fluid is withdrawn through the capillary feed channels of afountain pen or similar implement.

The embodiment of FIG. 1 is shown as being included in a cartridgebarrel unit intended for assembly with a fountain :pen Writing unit .38as illustrated in FIG. 2.

For this reason, the exterior surface of the body portion .12,is.pr0vided witha threadedarea ,40, or similar'means, adjacent ,itsforward end toallow direct attachment to the fountain pen writing unit38. Thus, the cartridge barrel unit 10 serves as the exterior barrel aswell as the fluidreservoir.

The writing unit 38 includes a generally cylindrical gripping portion 42which is formed preferably of an attractive and durable materialmatching or complement- .52 of the writing element or pen point 54. And,as indicated in FIG. 2, the pen point 54 is frictionally maintainedwithin the gripping portion 42 by the feed ba rt48.

To provide communication between the capillary fissure 5t and thereservoir, there is provided an insert 56 positioned in an axial feedaperture 58 which extends from the fissure 50 through the rearward endof the feed bar 48. This insert extends rearwardly beyondthe feedbar 4'8and terminates within 'a generally cylindrical pierce tube 64 having apierce point '62 defined by a tapered upper end. Provided by the insert56 is a capillary passage 64 arranged for the movement of fluid from thereservoir to the feed fissure 50, from where such fluid subsequently istransferred to the slit 5 2 of-the penpoint 54 for deposit duringwriting.

One of the features of the present invention is the elimination of'thenecessity of providing the usual comb cuts in order to retain fluidwhich might be-forced from the reservoir of a pen as a result ofatmospheric pressure or temperature changes.

In addition, there is no need to provide any type of passage for theexchange of air between the feed and reservoir since the flexible wallmember 20 is displaced within the body portion 12 to-followthe ink as itis withdrawn during writing and thereby reduce the volumetric capacityof the reservoir. These features eliminate the possibility of the entryof air into the reservoir, and the difliculties attendant thereto, aswell as greatly reducing the complexity and cost of manufacturing thefeed bar and its associated parts.

The heretofore described fountain pen construction is used by anindividual in the same manner as any other fountain pen. Thus, it doesnot require any special handling or attention on the part ofthe owner.When the implement is in writing use, *fluid is withdrawn'from thereservoir, as defined by the interior surface of the-flexible wallmember 2%, through the capillary passage 64 and the feed fissureStl,whereafter'it is transferred to the feed slit 52 of the pen point 54,and then-deposited on a writing surface, such as paper. As the flexiblewall member 20 follows the diminishing supply of ink, it gradually isdisengaged from the interior surface of the bodyportion 12, air pressurebeing exerted on its exterior surface through the vent 18 of the bodyportion 12.

The attraction between the flexible wall member 20 and the body portion12 prevents separation of-the wall member and body portion except as aresultof a slight negativepressure created in the reservoir upon thewithdrawal of fluid through the capillary passage edof the insert 56 andthe feed fissure 50 of the feed bar 43. While these capillary channelsare capable of producing only limited amounts of force, such force issufficient, in combination with air pressure, to draw the flexible wallmember away from the body portion 12 as represented in FIG. 2 of thedrawings.

Since only the substantially empty displaced portion of the wall member.20 is unsupported within the body portion 12,, the weight oftheremaining column of fluid doesnot cause any kinking orcreasing of thestill-filled portion of the wall member 20, therebypreventingentrapmentof part of the fluid behind a crease, or premature stoppage of the flowof fluid.

In the present invention, it is preferred to form the flexible wallmember 2%! directly in the'body portion .12 thereby eliminating theexpense of subsequent assembly of the individual parts.

The amount of attraction between the wall member and body portion may becontrolled in several ways, such as by the selection of materials to beused in the body portion and wall member, by providing slightirregularities such as grooves or a pebble surface on the interior ofthe body portion, or by using a release agent between the body portionand Wall member should the materials used therein exhibit a greateramount of attraction than is necessary.

Formation of the flexible wall member within the body portion 12 may beaccomplished by any one of several methods, such as by spraying thematerial of the Wall member within the body portion, or by a procedureknown as slush molding, which involves filling the body portion with aliquid plastic or rubber compound which is subsequently emptied exceptfor a thin layer adhering to the interior wall of the body portion. Theparticular process chosen depends somewhat upon the material used informing the flexible wall member 26 as certain materials lend themselvesbest to certain processes of handling, as is recognized readily by thosein the plastic and rubber fabricating field.

The embodiment of FIG. 1 may be formed by a threestep process such asthat shown in FIGS. 6, 7 and 8 of the drawings. This is a process bywhich the materials are sprayed within the body portion 12 as it iscarried from station to station on an automated indexing machine. Thebody portion 12 is first inserted into a holder or carrier 68 which isprovided with a centrally disposed plug 70 adapted to extend into andclose the vent 18, thus providing a substantially unbroken interior wallon the closed end 16 of the body portion 12.

The body portion 12 is moved to the first station on the indexingmachine as represented in FIG. 6, where a thin layer of a liquefiedadhesive or primer is sprayed on the interior surface of the bodyportion 12 to coat an annular recess 72 formed adjacent its open forwardend 14. Thespraying is accomplished by forcing the adhesive or primerthrough a plurality of small apertures disposed around the periphery ofa dispensing nozzle 74.

The body portion 12 is then moved to the next station, as illustrated byFIG. 7, at which time an elongated disspensing nozzle 76 is insertedtherein. The nozzle 76 is provided with a plurality of minute aperturesspaced over its entire surface so that a liquid material may be forcedtherethrough to provide an even coating of material on the interiorsurface of the body portion 12. For this particular step, a liquifiedsilicon rubber has been found to give good results not only from thestandpoint of ease of application but of subsequent performance as theflexible wall member 20 in the completed reservoir. Following the secondstep, it may be desirable to rotate the carrier 68 for a short time inorder to insure retention of an even thickness of material as it takesits initial set. Thus, the finished flexible wall member 211 willexhibit a uniform thickness throughout its length.

The third step in the procedure as represented by FIG.

I 8, involves the application of a catalyst to the thin layer of siliconrubber as formed during the second step, in order to complete itsvulcanization. As in the case of step 2, the catalyst is sprayed evenlyover the layer of silicon rubber through a plurality of apertures spacedover the surface of an elongated dispensing nozzle '78. Afterapplication of the catalyst, the body portion 12 may be removed from thecarrier 68 and prepared for further handling by the manufacturer.

' It is to be understood that various materials other than siliconrubber are useful in this invention, such as relatively resilient orelastic materials dissolved in a volatile vehicle, as well as materialssuch as latex dispersed in water. Such materials, of course, may requirea different method of application than that hereinabove described, aswill be understood readily by those in the art.

After the formation of the flexible wall member 20 has been completedthe cartridge unit may then be filled with ink or a similar liquidsubstance, and the open end '6 thereof sealed with the closure disc 28as described here'- tofore.

After the complete supply of Writing fluid has been depleted from thecartridge barrel unit 10, and the flexible wall member 20 completelycollapsed, it may be discarded and replaced by a fresh, factory filledunit. However, under certain circumstances, it may be desirable torefill the reservoir, which refilling may be done merely by forcingfluid under a light pressure through the above described fluid passages50 and 64. The pressure used in forcing the fluid through these channelsis suflicient to cause distention of the flexible wall member 20 intoits original intimate contact with the interior surface of the bodyportion 12.

It is understood that the term distention, as used herein, does notindicate any stretching or inflation of the flexible wall portion 20 butmerely the positioning thereof in its unstressed, neutral position.

The embodiment of FIG. 3, similar basically to the embodiment of FIG. 1is shown as being disposed in and partially assembled with a fountainpen having a writ ing unit assembly identical to that describedhereinabove. This modification includes a body portion or support 186which is formed preferably of a semi-rigid material such aspolyethylene. Formed within the body portion 100, in the mannerdescribed heretofore with respect to the embodiment of FIGS. 1 and 2, isa flexible or flaccid wall portion 162. As will be understood from theforegoing discussion of the embodiment of FIG. 1, the flexible wallmember is releasable from and displaceable within the body portion 1011to follow the ink and reduce the volumetric capacity of the reservoir asfluid is withdrawn therefrom during writing.

The forward ends 1114 and 1116 of the body portion and wall member 1612,respectively, are closed by a seal disc 1% molded of polyethylene orsimilar material and provided with a flange bonded to the body portion100 at its open forward end 104. The seal disc 1% is provided with anannular recess 112 defining a fluid discharge which is closed by a thindiaphragm member 114 which is readily pierceable by the pierce tube 116of the writing unit assembly 118. The insert 120 disposed within thepierce tube 116 provides a fluid passage 122 for communication betweenthe interior of the cartridge unit and a fluid feed path 124 formed inthe forward portion of the feed bar 126. Thus, after completing assemblyof the pen illustrated in FIG. 3 and during writinguse thereof, fluidwill be drawn from the reservior,

through the insert passage 122 and into the feed path 124, for transferto the pen point and subsequent deposit on a writing surface.

As clearly shown in FIG. 5 of the drawing, the body portion 100 isprovided with a plurality of longitudinally extending grooves 1125around its interior surface, in order to provide a larger area or"contact and a greater amount of adhesive attraction between the bodyportion 100 and the flexible wall member 102.

In order to allow displacement of the flexible wall portion 102 withinthe body portion 101 as fluid is with drawn from the reservoir duringwriting, air vent passages 126 and 128 are provided through the rearwardend of the pen barrel 120 and the body portion 100, respectively. Thevent 126 through the pen barrel 120 is defined by a tubular element 138provided on its forward end with a pierce point 132. The pierce point isadapted to break a diaphragm 134 which is formed in a second seal disc136 to close the vent 128 except upon assembly of the cartridge unitwith the fountain pen. One of the purposes of providing the diaphragm134 is to prevent inadvertent damage to the flexible wall member 102 asby the insertion of a pin or other sharp instrument through the vent 128prior to use of the cartridge unit.

In order to eliminate any possibility of rupture of the flexible wallmember 102 by the pierce point 132, the rearward end of the barrel 129is provided with an internally disposed forwardly facing shoulder 140which surrounds the tubular element 133 and which abuts the rearward oroutwardly facing surface of the second seal disc 136 thereby limitingthe amount of movement of the pierce point 132 through the vent 128during assembly of the barrel with the writing point assembly. Thisfeature is best shown in FIG. 4 of the drawings.

During formation of the flexible wall member 162 within the body portion1%, it is necessary to provide temporarily a closure member 142, seeFIG. 9, which conveniently may comprise a part of the holder or carrier144. The closure member 142 is sized so as to fit snugly within therearward end of the body portion ltiii and includes a generallysemi-spherical concave surface 146 in its lower end thereby forming awall portion against which the material of the flexible member 132 issprayed.

Prior to insertion of the closure member 1412, the lower end 146preferably is coated with a release agent so that it will readilyseparate from the rearward end of the flexible wall member 162 afterformation thereof. For the purpose of ejecting the body portion Mittafter completion of the wall member 102, the carrier or holder 144 isprovided with a ring 148 which is reciprocally movable relative to theclosure member 142 and sized to act against the rearward edge of thebody portion 1%.

The steps of formation of the wall member 102 within the body portion108 may be accomplished in substantialiy the same manner as thatdescribed previously with respect to the emobdiment of FIG. 1.Accordingly, a discussion of the steps involved will not be repeated atthis time.

it is to be understood that although only two embodiments of a fluidreservoir are illustrated and described herein for use with a fountainpen, this invention is not to be limited thereto as modificationsthereof may be provided and, likewise, the invention may be utilized inconnection with devices such as liquid adhesive dispensers and the like.Also, it is apparent that the flexible wall portion may be formed bymethods other than the one specifically described herein.

Accordingly, this invention is not to be limited to the embodimentsdescribed hereinabove, and it is contemplated, by the appended claims,to cover any such modifications as fall within the true spirit and scopeof this invention.

I claim:

1. A fountain pen comprising a fluid container and a writing unitassembly mounted forwardly of said fluid container, said fluid containerhaving a vented hollow body portion and a film-like layer of flexiblematerial forming a flaccid sack engaging the interior surface of saidbody portion, the interior surface of said sack defining a writing fluidreservoir, the exterior surface of said sac having an adhesive qualitycausing it to releasably stick to the interior surface of said bodyportion, said writing unit assembly having conduit means providing thesole means for fluid passage from said writing fluid reservoir, saidconduit means being small enough in cross-section to prevent passage ofair therethrough into said reservoir while writing fluid is disposedwithin said conduit means, the adherent attachment of said sack to theinterior surface of said body portion being sufficient to resistseparation thereof and the consequent free discharge of writing fluidthrough said conduit means under the influence of the normal weight ofthe fluid in the reservoir, and said sack being separable from anddisplaceable within said body portion to reduce the volumetric capacityof said reservoir in response to withdrawal of writing fluid from saidconduit by capillary action.

2. In a fountain pen, a writing fluid container comprising a hollow bodymember and a flexible wall member formed as a continuous film within andsubstantially covering the interior surface of said hollow body member,the interior surface of said wall member defining a reservoir forreceiving a column of writing fluid, the exterior surface of said wallmember having an adhesive quality causing it to releasably stick to theinterior surface of said body member, and capillary means for forciblywithdrawing writing fluid from said reservoir while preventing the entryof air thereinto, said container having a means providing atmosphericVenting to the exterior surface of said wall member, the adherentattachment of said wall member to the interior surface of said bodymember being suflicient to resist separation thereof and the consequentfree discharge of writing fluid through said capillary means under theinfluence of the normal weight of the column of writing fluid in thereservoir, the exterior surface of said wall member being progressivelydetached from the interior surface of said body member to reduce thevolumetric capacity of said reservoir in response to the Withdrawal ofwriting fluid from said reservoir by said capillary means.

3. In a fountain pen, a writing fluid container comprising a hollow bodymember and a flexible wall mem ber formed as a continuous film withinand substantially covering the interior surface of said hollow bodymember, the interior surface of said wall member defining a reservoirfor receiving a column of Writing fluid, the exterior surface of saidWall member having an adhesive quality causing it to releasably stick tothe interior surface of said body member, and capillary means forforcibly withdrawing writing fluid from said reservoir while preventingthe entry of air thereinto, said container having a means providingatmospheric venting to the exterior surface of said wall member, theinterior of said body member being provided with a surface conformationand finish which will cause said Wall member to be adherently attachedthereto suflicient to resist separation therefrom and the consequentfree discharge of writing fluid through said capillary means under theinfluence of the normal weight of the column of writing fluid in thereservoir, but which will nevertheless permit the exterior surface ofsaid wall member to be progressively etached therefrom against theresistance of the force of adhesion between said exterior surface andthe interior surface of said hollow body member to reduce the volumetriccapacity of said reservoir in response to the'forcible withdrawal ofwriting fluid from the reservoir by said capillary means.

References Cited by the Examiner UNITED STATES PATENTS 2,492,058 12/1949OConnor 45.4 2,499,771 3/1950 OCOnnor l2045.4 2,846,103 8/1958 Maxwell215-l1 2,876,113 3/1959 Barton 2l5 l1 X 2,987,209 6/ 1961 Leonard 215-11EUGENE R. CAPOZIO, Primary Examiner.

LAWRENCE CHARLES, JEROME SCHNALL,

Examiners.

1. A FOUNTAIN PEN COMPRISING A FLUID CONTAINER AND A WRITING UNITASSEMBLY MOUNTED FORWARDLY OF SAID FLUID CONTAINER, SAID FLUID CONTAINERHAVING A VENTED HOLLOW BODY PORTION AND A FILM-LIKE LAYER OF FLEXIBLEMATERIAL FORMING A FLACCID SACK ENGAGING THE INTERIOR SURFACE OF SAIDBODY PORTION, THE INTERIOR SURFACE OF SAID SACK DEFINING A WRITING FLUIDRESERVOIR, THE EXTERIOR SURFACE OF SAID SAC HAVING AN ADHESIVE QUALITYCAUSING IT TO RELEASABLY STICK TO THE INTERIOR SURFACE OF SAID BODYPORTION, SAID WRITING UNIT ASSEMBLY HAVING CONDUIT MEANS PROVIDING THESOLE MEANS FOR FLUID PASSAGE FROM SAID WRITING FLUID RESERVOIR, SAIDCONDUIT MEANS BEING SMALL ENOUGH IN CROSS-SECTION TO PREVENT PASSAGE OFAIR THERETHROUGH INTO SAID RESERVOIR WHILE WRITING FLUID IS DISPOSEDWITHIN SAID CONDUIT MEANS, THE ADHERENT ATTACHMENT OF SAID SACK TO THEINTERIOR SURFACE OF SAID BODY PORTION BEING SUFFICIENT TO RESISTSEPARATION THEREOF AND THE CONSEQUENT FREE DISCHARGE OF WRITING FLUIDTHROUGH SAID CONDUIT MEANS UNDER THE INFLUENCE OF THE NORMAL WEIGHT OFTHE FLUID IN THE RESERVOIR, AND SAID SACK BEING SEPARABLE FROM ANDDISPLACEABLE WITHIN SAID BODY PORTION TO REDUCE THE VOLUMETRIC CAPACITYOF SAID RESERVOIR IN RESPONSE TO WITHDRAWAL OF WRITING FLUID FROM SAIDCONDUIT BY CAPILLARY ACTION.